1. Field of the Invention
The present invention relates to a method of doubling the frame rate of video signals, and more particularly relates to a method for frame rate up conversion.
2. Description of the Related Art
To display the full frame rate at the receiver side, a recovery mechanism, called frame rate up conversion (FRUC), is needed to re-generate the skipped frames and to reduce temporal artifacts. Generally, FRUC is the process of video interpolation at the video decoder to increase the perceived frame rate of the reconstructed video.
In FRUC, interpolated frames are created using received frames as references. Currently, systems implementing FRUC frame interpolation include approaches based on motion compensated interpolation and the processing of transmitted motion vectors. FRUC is also used in converting between various video formats.
Many FRUC algorithms have been proposed, which can be classified into two categories. The first category interpolates the missing frame by using a combination of received video frames without taking object motion into account. Frame repetition and frame averaging methods fit into this class. FIG. 1(a) shows the value of each pixel in an interpolated frame determined by a frame repetition method. The value of each interpolated pixel in an interpolated frame at time Tn is the same as the value of each corresponding current reference pixel in a current frame at time Tn+1 rather than a previous frame at time Tn−1. Furthermore, FIG. 1(b) shows the value of each pixel in an interpolated frame determined by a frame averaging method. The value of each interpolated pixel in an interpolated frame at time Tn is an average between that of each corresponding current reference pixel in a current frame at time Tn+1 and that of each corresponding previous reference pixel in a previous frame at time Tn−1. The drawbacks of these methods include the production of motion jerkiness, “ghost” images and blurring of moving objects when there is motion involved.
The second category is more advanced compared to the first category, and utilizes the transmitted motion information, the so-called motion compensated (frame) interpolation (MCI). Although MCI offers some advantages, it also introduces unwanted areas such as overlapped (multiple motion trajectories pass through this area) and hole (no motion trajectory passes through this area) regions in interpolated frames. The interpolation of overlapped and hole regions are a major technical challenge in conventional motion compensated approaches. On the other hand, the drawbacks of methods related to MCI include an increase in the complexity of interpolation operations.
Accordingly, there is a need to overcome the issues noted above. That is, an uncomplicated and high visual quality method for frame rate up conversion is urgently needed in various video applications.